feat(cli): hand off onboarding to your coding agent

[bjoaquinc]

Overview

Reworks the dlthub-start onboarding so the CLI sets the workspace up and then hands off to your coding agent, instead of running the sample pipeline and opening the dashboard itself. Also tightens the setup output and copy so the run reads cleanly.

Changes

Flow (cli.py)

• After scaffolding, installing deps, logging in, and connecting a playground workspace, the CLI hands off to the chosen agent rather than running load_sample_shop / opening the dashboard.
• Agent selection and launching are now separate steps: pick an agent, then choose to launch it (it deploys and runs the sample pipeline via the deploy-run-sample-pipeline skill) or skip and get the prompt printed + copied to paste into an agent yourself.
• On login / playground-connection failure the CLI still hands off — with a prompt asking the agent to help resolve the error (deps are installed, so the dlthub CLI works). uv sync failure still exits with the error (no CLI = no hand-off).
• Collapsed scaffold + uv sync into one step and login + playground connection into another; login runs quietly (output surfaces only on error).

Copy (strings.py)

• One canonical hand-off prompt (launched / pasted / non-TTY) embedding the skill's absolute path so the agent finds it from any cwd; the launch-plan preview shows a short workspace-relative path.
• Launch plan states what will happen ("let {agent} deploy and run…" / "Setup hit an error — let {agent} help resolve it…"), self-documenting launch choices, and an outcome-matched closing panel ("You're all set" / "Almost there").
• Removed stale "build dlt pipelines / first run / open the dashboard" wording and an orphaned string.

Other modules

• display.py: print_next_steps takes agent_prompt + panel_title.
• prompts.py: confirm() supports custom yes/no labels.
• config.py: added AGENT_SKILLS_DIR (drift-checked against the scaffold); bumped WORKBENCH_REF.

Docs

• Updated README, CONTRIBUTING, the scaffold README, the workspace-here Makefile help, the pyproject description, and the CHANGELOG to match the new flow; fixed stale --yes/--skip-uv-sync references (now --setup-only/--scaffold-only) and the codex .agents/ directory.

Bundled workbench

• Regenerated _agents/** from the bumped WORKBENCH_REF: the toolkit-dispatch skill is now dlthub-router, which routes to and installs the right workflow toolkit on demand. Refreshed the scaffold uv.lock (dlt 1.28.1).

Tests

• New/updated unit tests across test_cli.py, test_display.py, test_config.py, test_prompts.py covering the hand-off paths (launch / decline / unlaunchable agent / non-TTY / login-failure resolve), the outcome panel titles, the quiet login, and the AGENT_SKILLS_DIR mapping.
• 133 passed; ruff and mypy clean.
• Smoke-tested make workspace-local end-to-end (scaffold → quiet login/connect → hand-off).